摘要 :
The comparative analysis of spectral and correlation properties of complex signals based on linear discrete frequency modulation and frequency modulation.
摘要 :
The comparative analysis of spectral and correlation properties of complex signals based on linear discrete frequency modulation and frequency modulation.
摘要 :
The detection and parametric estimation of low-SNR radar signals, particularly linear frequency modulated (LFM) radar signals, is a problem of considerable interest. In prior work, this problem has been investigated using various ...
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The detection and parametric estimation of low-SNR radar signals, particularly linear frequency modulated (LFM) radar signals, is a problem of considerable interest. In prior work, this problem has been investigated using various signal processing techniques, such as maximum likelihood estimation, fractional Fourier transform and Wigner-Ville-based methods, to analyze the signal parameters of a complex linear frequency modulated signal. Other work has focused on applying deep learning to automatically recognize various radar waveform types and their features, such as linear frequency modulation (LFM), Barker code and rectangular waveforms. In this paper, we investigate this problem from a machine learning perspective for multiple LFM radar signals given a priori information. We explore the use of naive Bayes, support vector machine and neural network classifiers to identify the LFM chirp rate, out of a set of known chirp rates, from a specific radar emitter under varying SNR conditions. Simulation results demonstrate the viability of this technique to identify the radar LFM mode in very low signal-to-noise ratio conditions down to -20 dB where using existing approaches (e.g., Wigner-Ville) fail.
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摘要 :
The detection and parametric estimation of low-SNR radar signals, particularly linear frequency modulated (LFM) radar signals, is a problem of considerable interest. In prior work, this problem has been investigated using various ...
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The detection and parametric estimation of low-SNR radar signals, particularly linear frequency modulated (LFM) radar signals, is a problem of considerable interest. In prior work, this problem has been investigated using various signal processing techniques, such as maximum likelihood estimation, fractional Fourier transform and Wigner-Ville-based methods, to analyze the signal parameters of a complex linear frequency modulated signal. Other work has focused on applying deep learning to automatically recognize various radar waveform types and their features, such as linear frequency modulation (LFM), Barker code and rectangular waveforms. In this paper, we investigate this problem from a machine learning perspective for multiple LFM radar signals given a priori information. We explore the use of naive Bayes, support vector machine and neural network classifiers to identify the LFM chirp rate, out of a set of known chirp rates, from a specific radar emitter under varying SNR conditions. Simulation results demonstrate the viability of this technique to identify the radar LFM mode in very low signal-to-noise ratio conditions down to -20 dB where using existing approaches (e.g., Wigner-Ville) fail.
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摘要 :
This paper describes the design, simulation and practical results of a phase modulator based in an hybrid coupler and two varactor diodes in the band from 2.0 GHz to 3.0 GHz for TTC proposes. A minimum modulation index of 1.22 was...
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This paper describes the design, simulation and practical results of a phase modulator based in an hybrid coupler and two varactor diodes in the band from 2.0 GHz to 3.0 GHz for TTC proposes. A minimum modulation index of 1.22 was obtained at the highest frequency to 1.57 at the lowest. This modulator consist of a two stages hybrid coupler with varactor diodes. Simulation is performed using ADS 2016.01. Even both varactor diodes are feed by the same modulation signal, each of them has his own voltage input for correct varactor impairments. In the measures, excellent isolation is achieved for the 1
st
and 4th port of the ring.
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摘要 :
This paper describes the design, simulation and practical results of a phase modulator based in an hybrid coupler and two varactor diodes in the band from 2.0 GHz to 3.0 GHz for TTC proposes. A minimum modulation index of 1.22 was...
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This paper describes the design, simulation and practical results of a phase modulator based in an hybrid coupler and two varactor diodes in the band from 2.0 GHz to 3.0 GHz for TTC proposes. A minimum modulation index of 1.22 was obtained at the highest frequency to 1.57 at the lowest. This modulator consist of a two stages hybrid coupler with varactor diodes. Simulation is performed using ADS 2016.01. Even both varactor diodes are feed by the same modulation signal, each of them has his own voltage input for correct varactor impairments. In the measures, excellent isolation is achieved for the 1
st
and 4th port of the ring.
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摘要 :
In this paper, the variation of side lobe level (SLL) of ‘optimized uniformly excited time-modulated linear antenna array’ (OUE-TMLAA) with different number of antenna elements is presented. To realize the optimized array patter...
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In this paper, the variation of side lobe level (SLL) of ‘optimized uniformly excited time-modulated linear antenna array’ (OUE-TMLAA) with different number of antenna elements is presented. To realize the optimized array patterns of the arrays, sideband levels (SBLs) is suppressed to below −30 dB and the increase on first null beam width (FNBW) is restricted within 35% of that of the ‘uniformly excited conventional linear antenna arrays’ (UE-CLAAs) while the peak SLL is reduced as low as possible. A differential evolution (DE) based optimization method is employed where only the on-time sequence of the antenna elements are considered as the optimization parameter vectors. By taking the antenna arrays of wide range of number of antenna elements, starting from 10 to 500 and using the average results of 20 trials of each OUE-TMLAA, a representative plot of the variation of average SLLs with the number of antenna elements is presented.
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摘要 :
In this paper, the variation of side lobe level (SLL) of ‘optimized uniformly excited time-modulated linear antenna array’ (OUE-TMLAA) with different number of antenna elements is presented. To realize the optimized array patter...
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In this paper, the variation of side lobe level (SLL) of ‘optimized uniformly excited time-modulated linear antenna array’ (OUE-TMLAA) with different number of antenna elements is presented. To realize the optimized array patterns of the arrays, sideband levels (SBLs) is suppressed to below ?30 dB and the increase on first null beam width (FNBW) is restricted within 35% of that of the ‘uniformly excited conventional linear antenna arrays’ (UE-CLAAs) while the peak SLL is reduced as low as possible. A differential evolution (DE) based optimization method is employed where only the on-time sequence of the antenna elements are considered as the optimization parameter vectors. By taking the antenna arrays of wide range of number of antenna elements, starting from 10 to 500 and using the average results of 20 trials of each OUE-TMLAA, a representative plot of the variation of average SLLs with the number of antenna elements is presented.
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摘要 :
In ultrasound harmonic imaging with linear frequency modulated (LFM) excitation, the sidelobes level in the compressed harmonic signal can be reduced by applying a windowing function. Windowing on the transmitting signal causes re...
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In ultrasound harmonic imaging with linear frequency modulated (LFM) excitation, the sidelobes level in the compressed harmonic signal can be reduced by applying a windowing function. Windowing on the transmitting signal causes reduced penetration depth, whilst windowing on the receiving side results in reduced signal-to-noise ratio (SNR) gain and axial resolution. To optimize the transmitting signal energy and the SNR gain with reduced sidelobes level in the compressed harmonic signal, the use of nonlinear frequency modulated (NLFM) signals are proposed. The NLFM signal and associated second harmonic matched filter are designed using an analytical approach to minimise correlation errors. In all simulations and experiments, the NLFM signal performance is compared with the reference LFM signal of similar sweeping bandwidth and duration. The results indicate at least a 15 dB reduction in the peak sidelobes level of the NFLM compressed second harmonic signal with comparable axial mainlobe width when compared with the LFM compressed harmonic signal.
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摘要 :
In ultrasound harmonic imaging with linear frequency modulated (LFM) excitation, the sidelobes level in the compressed harmonic signal can be reduced by applying a windowing function. Windowing on the transmitting signal causes re...
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In ultrasound harmonic imaging with linear frequency modulated (LFM) excitation, the sidelobes level in the compressed harmonic signal can be reduced by applying a windowing function. Windowing on the transmitting signal causes reduced penetration depth, whilst windowing on the receiving side results in reduced signal-to-noise ratio (SNR) gain and axial resolution. To optimize the transmitting signal energy and the SNR gain with reduced sidelobes level in the compressed harmonic signal, the use of nonlinear frequency modulated (NLFM) signals are proposed. The NLFM signal and associated second harmonic matched filter are designed using an analytical approach to minimise correlation errors. In all simulations and experiments, the NLFM signal performance is compared with the reference LFM signal of similar sweeping bandwidth and duration. The results indicate at least a 15 dB reduction in the peak sidelobes level of the NFLM compressed second harmonic signal with comparable axial mainlobe width when compared with the LFM compressed harmonic signal.
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